J.U.C-FutureTask

创建线程有两种方式:继承Thread和实现Runnable接口
但是都有一个共同的缺陷:

执行完任务后，无法获取执行结果
通过Callable和Future可以得到任务执行完之后的结果

• Callable与Runnable接口对比

Callable是泛型的接口,其中有一个call函数, call函数的返回类型就是创建Callable时传进去的类型

• Future也是以个接口, 对于任务可以进行取消, 查询是否执行完成等, 可以监视目标线程调用call的情况

package io.haitaoc.concurrency.example.aqs;

import java.util.concurrent.*;

public class FutureExample {

    // 返回类型是String
    static class MyCallable implements Callable<String> {

        @Override
        public String call() throws Exception {
            System.out.println("do something in callable");
            Thread.sleep(5000);
            return "Done";
        }
    }

    public static void main(String[] args) throws InterruptedException, ExecutionException {
        ExecutorService executorService = Executors.newCachedThreadPool();
        // 通过Future接收另外一个线程计算的结果
        Future<String> future = executorService.submit(new MyCallable());
        System.out.println("do something in main");
        Thread.sleep(1000);
        String result = future.get();
        System.out.println(result);
    }
}

• FutureTask父类是RunnableFuture, 执行Callable类型的任务,并且有Future的特性

package io.haitaoc.concurrency.example.aqs;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;

public class FutureTaskExample {

    public static void main(String[] args) throws InterruptedException, ExecutionException {
        FutureTask<String>  futureTask = new FutureTask<String>(new Callable<String>() {
            @Override
            public String call() throws Exception {
                System.out.println("do something in callable");
                Thread.sleep(5000);
                return "Done";
            }
        });

        // 启动任务
        new Thread(futureTask).start();
        System.out.println("do something in main");
        Thread.sleep(1000);
        String result = futureTask.get();
        System.out.println(result);
    }
}